DESCRIPTION: The long range objective of this research project is to identify genes that influence alcohol preference. The focus of this proposal is to identify the genes that influence alcohol preference located within the chromosomal regions (quantitative trait loci) that were identified in the previous proposal. Numerous family and twin studies in the past years have shown that genetic factors are involved in the genesis of alcoholism. Identification of the genes underlying alcohol-drinking behavior would help our understanding of the mechanisms of this disease and the approaches that need to be taken for treatment and prevention. To better understand the genetics of alcoholism and alcohol preference, a series of studies using complementary inbred and noninbred rat lines derived from two founder stocks (Wistar and N/Nih) and selected by two different paradigms will be employed. Congemc strains in the P (alcohol preferring)/NP (alcohol nonpreferring)for the chromosome 4QTL (lod score = 9.2) will be completed to narrow the critical region to 2.5 cM. The extensive informatic resources available for the rat will be utilized to identify and prioritize candidate genes in the 2.5 cM region for further study. Complementary molecular techniques, nucleotide sequencing and Real-Time polymerase chain reaction, will be employed to identify the candidate genes that warrant further evaluation. Congemc and inbred strains will be compared to maximize our ability to detect meaningful expression and sequence differences. Candidate genes for alcohol preference identified through both QTL and knock-out studies in the mouse will be compared between the inbred P and NP strains by sequence analyses. The critical interval of the HAD1 (high alcohol drinking)/LAD1 (low alcohol drinking) QTLs on chromosomes 5,10,12, and 16 will be narrowed by placing additional markers in the regions. The HAD2/LAD2 rat lines, also derived from the heterogeneous N/Nih stock rats, will be used to confirm the QTLs identified in the HAD 1/LAD 1 lines. Five hundred noninbred HAD2xLAD2 F2 will be tested for linkage to the four chromosomal regions. Congenic lines will be made for each confirmed QTL using the inbred HAD/LAD strains to further narrow the critical region where the alcohol preference gene(s) lies. Candidate genes within the confirmed QTL regions will be identified and prioritized for sequencing using the rat informatic resources.